A variety of different end products are manufactured in the above-mentioned way. Examples of end products include truck tarps, boat tarps, tarpaulins, tents, doors, fabric ceilings, inflatable products, liquid tanks, advertising signboards, sun shading, projection screens, sports facilities, storage facilities, tribune roofs, oil containment booms, valve drums, lifesaving equipment, rescue stretchers, water beds, bathing pools, etc.
High-frequency welding of polymer material is a well-known method that has been used since the 1940ies and has now been greatly developed and refined in terms of control processes, material combinations and design of process tools, such as electrodes. By means of state-of-the art process methods it is possible to obtain even, leak-proof and durable welding seams for even the widest variety of uses, such as the ones mentioned above.
In principle, high-frequency welding of two layers of polymer material is performed such that both materials are, in an overlapping welding area, pressed together between two welding electrodes or between a welding electrode and a ground plane and are exposed to a high-frequency electromagnetic field, usually 27.12 MHz. The combination of the heat generated and pressure brings about a welding seam. Four important factors that influence the final welding result are compression pressure, welding effect, welding time, and cooling time. Those parameters may be adjusted and combined in various ways to arrive at an optimal welding result for a specific material or a specific material combination.
Usually high-frequency welding is used for joining of polyvinyl chloride (PVC) and polyurethane (PU).
Obviously, it is important in the context of many of the end products listed above that they are leak-proof.
It is a substantial problem in the manufacture of said end products that, in addition to being joined, the constituent construction parts are also to be anchored in the bearing structures, and that it has so far been very difficult, cumbersome, and time-consuming to locate fastener means by way of high-frequency welding of weldable polymer material, while simultaneously applying the fastener means such that the structure becomes leak-proof. Examples of hitherto known methods of anchoring combined construction parts in bearing structures include tailored pockets on the construction parts, said pockets being intended for the introduction of carrier lists that are subsequently coupled to bearing structures. The difficulty of anchoring, in a simple and in all respects satisfactory manner, combined construction parts in bearing structures has lead to the end products becoming complex and expensive to manufacture and assemble.
For a long time there has been a very great need, in the building up of end products of the above-mentioned kind, for simplified solutions for the anchoring to bearing structures by means of units joined by high-frequency welding.
There is also a need for making manufacturing and mounting processes more efficient, eg within car manufacturing or within the building industry, to reduce the time consumption involved in the mounting and/or manufacturing processes.